Roller bearings have a larger load capability for radial load than ball bearings. A conical roller bearing into which truncated cone-shaped rollers (conical rollers) are embedded as rolling elements, is capable of supporting a combined load of radial load and axial (thrust) load, and thus is widely used at rotation support parts of drive devices, gear reducers, power transmission devices, and the like in various mechanical systems such as automobiles, rail vehicles, and construction machines, and the like. A spherical roller bearing (automatic self-aligning roller bearing) into which barrel-shaped rollers (spherical rollers) are embedded as rolling elements, has the advantage of being usable for its self-aligning property even if an outer ring and an inner ring are inclined due to an attachment error or shock load, and thus is widely used at rotation support axis parts of various industrial mechanical systems and the like under vibration and shock load.
Cages used for such roller bearings are generally press cages that are formed by pressing a steel plate such as a cold-rolled steel plate or a hot-rolled steel plate. Finished products are fabricated from disc-shaped intermediate materials formed by pressing and punching a metal plate through a large number of press steps (refer to Patent Document 1, FIGS. 5 and 6, for an example of a conical roller bearing cage, and refer to Patent Document 2, FIG. 16, for an example of a spherical roller bearing cage).
In addition, structures of press cages frequently used as cages for spherical roller bearings are broadly classified into: (1) a press cage that is formed from a bowl-shaped main part including pockets for storing spherical rollers and a small diameter-side inward flange extended inward in a radial direction from a small diameter-side end edge of the main part, the main part being positioned on the radially outer side of the pitch circle diameters of the spherical rollers, that is, the rotation center axes of the spherical rollers reside on the inner diameter-side across the column parts (hereinafter, referred to as “bowl-shaped cage.” For example, refer to Patent Documents 3 and 4); and (2) a press cage that is formed from a conical main part including pockets for storing spherical rollers, a large diameter-side outward flange extended outward in a radial direction from a large diameter-side end edge of the main part, and a small diameter-side inward flange extended inward in a radial direction from a small diameter-side end edge of the main part, or a conical main part including pockets for storing spherical rollers and a large diameter-side outward flange extended outward in a radial direction from a large diameter-side end edge of the main part, the main part being positioned on the radially inner side of the pitch circle diameters of the spherical rollers, that is, the rotation center axes of the spherical rollers reside on the outer diameter-side across the column parts (hereinafter, referred to as “outward flange-type cage.” For example, refer to Patent Documents 2 and 5).
The outward flange-type cage is pressed into an integral form including the large diameter-side outward flange, and thus is high in rigidity and load capacity.
In addition, there is also a conical roller bearing cage that is manufactured by fabricating separately a first member including a small-diameter ring part and a column part and a second member including a large-diameter ring part, and then joining and fixing the first and second members by laser welding (for example, refer to Patent Document 6).
Here, the first member is fabricated through a first punching step at which a circular material is formed from a belt-shaped plate-like material, a second punching step at which an intermediate material is formed by punching out a plurality of fan-shaped parts from the circular material, a surface pressing step at which tapered conical roller abutment surfaces are formed at both edges of an upper surface of a column-formed plate part in the intermediate material, a folding step at which a base end of the column-formed plate part is folded and erected, and a third punching step at which an inner peripheral portion of central plate is cut in a circular shape. The second member is fabricated through an abutment portion processing step at which abutment portions for abutment and joint with leading ends of the column parts of the first member are formed in a band-like elongated member, and a deforming and fixing step at which the elongated member is cut in a predetermined length and deformed in a circular shape, and ends of the cut portions are joined and fixed to each other by joining means such as welding or the like (for example, refer to Patent Document 6, FIGS. 6 and 18 to 20).
Further, there is a conical roller bearing cage that is manufactured by fabricating separately a first member including a large-diameter ring part and a column part and a second member including a small-diameter ring part, and joining and fixing the first and second members by laser welding (for example, refer to Patent Document 6).
Here, the first member is fabricated through a first punching step at which a belt-like plate-shaped material is punched into a disc-shaped central portion and a plurality of fan-shaped portions continued to the central portion to form an intermediate material, a surface pressing step at which an intermediate material is formed by forming tapered conical roller abutment surfaces at both edges of a lower surface of a column-formed plate portion formed in the intermediate material, a folding step at which a base end of the column-formed plate portion is folded and erected, and a second punching step at which an outer peripheral portion of the intermediate material is cut into a circular shape. The second member is fabricated through an abutment portion processing step at which abutment portions for abutment and joint with leading ends of the column parts of the first member are formed in a band-like elongated member, and a deforming and fixing step at which the elongated member is cut in a predetermined length and deformed in a circular shape, and ends of the cut portions are joined and fixed to each other by joining means such as welding or the like (for example, refer to Patent Document 6, FIGS. 1 to 6).
Besides, to join and fix together the first and second members (or their equivalents), there are methods using rivets to swage the axis ends, which are not used for press cages though (for example, refer to Patent Documents 7 and 8).